Thanks for all the thoughts guys. 1" plus the fiber won't fit. I was thinking the fiber would be good because it conforms the the irregular shapes and gets rid of air spaces.
The reflectix could possibly help with thermal bridging, as it would be the only insulation on the actual framing.
Poky, it was actually your buildup that got me thinking of using rigid foam. Thanks for the inspiration! And using a table saw to cut the foam, I hadn't considered that option.... good to know!
Klahanie, yes, we did fix the roof leak by simply resealing all the roof screws with 3m 4200.
Huh, that info on needing an air gap with Reflecix is very interesting. My conclusion would be that there is no point in putting it behind the 1/8" wall boards, as they would be touching the Reflectix. However, using it on the ceiling would be useful as heat would radiate back down through the thin fabric covering it.
More pix and details to come, eventually!